Trunk hunting final selector



April 30, 1957 w. w. PHARIS v 2,790,852

TRUNK HUNTING FINAL SELECTOR Filed May s, :956- l s sheets-sheet 1y TUB-*Erl frei-@ x kcosas I CUT OFF I p (-1 "/m--l I SD /7 H J l me) ce2 t cal sus sn4 f Pn-f/ cmd me) /SONIB INVENTOR. WILLIAM W. PHARI S AGENT April 30, 1957 w. w. PHARIS TRUNK HUNTING FINAL SELECTOR N SVSheqtS-Shee 2 Filed May 3, 1956 mm: xf

llmnn Filed May 5, 1956 w. w; PHARls TRUNK HUNTING FINAL SELECTOR 5 Sheets-Sheet 3 United States Patent TRUNK HUNTING FINAL SELECTOR William W. Pharis, Rochester, N. Y., assignor to General 1 Dynamics Corporation, Rochester, N. Y., a corporation of Delaware Application May 3, 1956, Serial No. 582,392

8 Claims. (Cl. 179-18) connections between `calling and called station lines in response to the dialing of two or more digits by a calling station. Frequently included in these selectors is the provision for groups of so-called switchthrough type trunks which are accessible on the same basis as called station lines. In such selectors, an arrangement is sometimes provided for providing access to a group of cutthrough type trunks in response to the dialing of a single digit by a calling subscriber.

In order to meet certain system requirements, it may be advantageous in such a selector to provide access to cut-through type `trunks in response to the dialing of two digits. The problems created by the inclusion of two digit switchthrough and cut-through and also single digit cut-through type trunks within the same final selector is further complicated when the selector is arranged for restricted access to certain trunk groups from calling lines of a particular type or class.

' Accordingly, it is an object of my invention to provide a new and improved final selector.

Another object of my invention is to provide a new and improved one and two digit responsive final selector.

Another object of my invention is to provide a new and improved one and two digit responsive nal selector capable of trunk hunting.

Another object of my invention is t-o provide a newY and improved one and two digit responsive nal selector capable of switchthrough and cut-through type operation.

Another object of my invention is to provide a new and improved restricted service type final selector.

An object of my invention is to provide a new and improved one and two digit responsive final selector capable of switchthrough and cut-through type operation which is arranged for restricted service.

Another object of my invention is to provide a new and improved restricted service type final selector wherein restricted signals may be transmitted from a calling line circuit over a path including the talking channel of the connector.

A feature of the connector forming the preferred embodiment of my invention is the provision for one and two digit type trunk hunting followed by cut-through type operation in first and second particular levels respectively, and for two digit trunk hunting followed by switchthrough operation on other levels where the rst and second levels are reserved for terminating trunks and the other levels may be used for terminating subscriber lines as well as groups of trunks.

I accomplish these and `other objects by providing a telephone system of the private branch exchange type having a calling line, final selector and linel finder means 2,790,852 Patented Apr. 30, 1.957

for extending a connection from the line to the selector. The iinal selector has incoming and outgoing ends and includes a speech transmission channel. The incoming end of the channel to which the line is connected includes a direct current signaling circuit. The outgoing end of the selector includes a set of wipers. Certain wipers of the set are connected to the outgoing end of the channel. The set also lincludes a test Wiper. Means such as blocking capacitors is normally effective for separating the signaling circuit from the outgoing end of the channel. n

The selector includes lirst and second particular levels and other levels to any of which the wiper set may be advanced from its normal position in a primary motion. The wiper set may then be advanced into a selected level in a secondary motion. Each level includes a plurality of sets of terminals. Each terminal set is used for terminating succeeding equipment and includes speech transmission channel terminals for engagement by the channel wipers and a test terminal for engagement by the test wiper. Provision is made for applying a busy indicating potential to the test terminal of a set when the equipment connected to that particular set is in'use. All the terminal sets within the first level are in a single group. Similarly, certain successive ones of the terminal sets within the second particular level and any one of the other levels may be arranged in one or more such group per level.

Operation of the line finder means and the resulting extension of a connection to the selector seizes the selector and makes the signaling circuit operative. A rst directive operation of the signaling circuit is effective for causing well known means within the selector to advance the wiper set in its primary direction in order to select one of the levels. Well known means within the selector operative in response to seizure of the selector is effective following the operation of the primary means for preparing other well known means to advance the wiper set in its secondary direction under the control of the signaling circuit. Thus, in the event that the second or one of the other levels is selected, a second operation of the signaling circuit is effective for advancing the wiper set into engagement with one of the terminal sets within the selected level. Following the conclusion of the transmission of the second signal, means within the selector is effective for releasing the preparing means. Means effective in the event that one of the other levels has been selected and operative in response to the release of said preparing means is elective for thereafter rendering busy test means and switchthrough means operative. The presence of a busy indicating potential on the test terminal of the engaged set is effective for operating the busy test means andthereby transmitting a busy indicating signal to the calling line. In the absence of such a potential the switchthrough means operates for the purpose of completing a connection including the speech transmission channel and the blocking means between the calling line and the channel terminals of the set engaged by the wiper set.

The selector .also includes other means for operating the secondary advancing means in order to cause the advance of the wiper set from a busy terminal set to the next succeeding terminal set withina group. This other means may be controlled over any of a irst, second, or third circuit, all of which are completed from busy potential on the test terminal of the set engaged by the wiper set. Thus I have provided lirst means efective in rseponse to the operation of the above referred to busy test means in operated condition, the release'of the preparing means, and to the selection of any one of the" other levels for extending the rst circuit to the test terminal of the set included in a group. The other secfrom-conductor MG through make contacts SD3 and the winding of relay PH to battery. Relay PH operates at this time.

The operation of relay RD also prepares at make contacts RD2 a circuit for operating busy test relay BT and opens at break contacts RD6 an energizing circuit for release magnet R.

Advancing the ,final selector Following the establishment of a connection from a calling line to the incoming end iinal selecto-r and to tre seizure of the final selector in the above described man ner, the transmission of the series of signals from the station, such as A, connected to the calling line is effective for operating a signaling circuit comprising the windings of relay CB which are connected over the above-traced operating circuit to the incoming end of the iinal selector. The signals comprise trains of one or more impulses caused by the repeated opening of the dial break contacts D10 at calling line station A. Relay CB releases in responseto each opening of contacts D10. The resulting impulsing operation of relay CB is eliective for causing means including primary magnet P and secondary magnet S within the iinal selector to advance the wiper set comprising wipers TS, RS, SS and HSS, which are a part of the outgoing end of the nal selector, in primary and secondary directions respectively. By its primary advance, the wiper set selects a level of terminal sets. The secondary direction advance is eiective to place the wipers of the set in engagement with corresponding'terminals in one of the sets within the selected level.

Primary movement.-Assuming that it is desired to extend a call from station A to another station such as C, signals effective for moving the wiper set in the pri-l mary and secondary directions into engagement with the terminal set associated with line circuit LC12 and line 12 are transmitted from the dial at calling station A. In response to each release of relay CB during the iirst impulsing operation and to the operation of relay PD, a circuit is completed for energizing the primary advancing means including magnet P. Each energization of magnet P is eiiective to advance the wiper set one step in its primary direction. Relay RD is a slow release type, so that the momentary opening of its operating circuit at contacts CB2 during the impulsing operation of relay CB does not release relay RD. The exact manner in which the primary advance of the wiper set is accomplished is next described. During each release of relay CB during the transmission of the first series of impulses, a circuit for energizing magnet P is completed as follows: from ground through break contacts CT13 and CB1, make contacts RDS and BD6, and the magnet P to battery.

Also completed at the same time is an obvious holding circuit through winding 2 of relay PD which is in parallel with magnet P. The establishment of the holding circuit for relay PD, a slow release type, prevents the release of that relay during the transmission of the signal even fthough the above described operating circuit including Winding 1 is opened at contacts PONlil. An opening of the above described operating circuit for relay PD which includes winding 1 is made upon the advance of the wiper set away from its normal position by the operation of primary ot`f-normal means including contacts PON10. Thus relay PD is held operated until'the transmission of the iirst train of impulses has been completed; at that time relay CBcomes to rest in its operated condition to open the operating circuit for magnet P and the holding circuit for relay PD at contacts CB1. Relay PD there upon releases.

`Secondary movement-At this time the wiper set comprising wipers TS, RS, SS and HSS has been advanced to a pointlopposite oneof the levels in which station lines, such. as C, are terminated. The release of relay PD is effective for opening the above traced energizing circuit for magnet P and winding 2 of relay PD at make con-v tacts PD'and for preparing a circuit-,for energizing secondary magnet S by closing contactsPD7.-

Thereafter, the transmission ofthe second train `of impulses causes a second impulsing operation of relay CB in order to transmit a series of impulses to the secondary advancing means including magnet S. The energizing circuit for magnet S is traced from ground through break contacts CT13 and CB1, make contacts RDS, break contacts PD7, make contacts SD6 and PHS and magnet S to battery. An obvious holding circuitfor relay SD is traced from the winding of magnet S through-'make con-y tacts SD,u and winding 2 of relay SD to battery. Thus, relay SD is maintained in its operated condition throughout the transmission of the second train of impulses even though the above traced operating circuit comprising winding 1 of relay SD is opened. Upon the vadvance of the wiper set into engagement with the first set of terminals within the selected level secondary off-normal means including springs SONl are opened to interrupt the previously traced operating circuit comprising winding 1 of relay SD. Thus, upon the completion of the transmission of the second impulse train, when relay CB comes to rest in its operated condition, the energizing circuit of magnet S and the holding circuit of relay SD are opened at break contacts CB1. Relay SD thereafter' releases.

In addition to advancing the main wiper set comprising TS, RS, SS and HSS in the primary direction,the operation of the magnet P is effective for advancing level markl ing wipers X and XX across banks of level'indicating terminals XB and XXB, respectively. The engagement by these wipers of the corresponding terminals is-efective for indicating to which of the levels the main wiper set has been advanced. ln the preferred embodimentof my ini vention, l have shown a final selector switcliin which subscribers lines are terminated in the fifth "through eighth levels inclusive. Such levels vare characterized by connection of the XXB bank terminal through wiper HSS by way of B wiring and contacts BTS for purposes which are to be explained presently. j

Busy test2-When the wiper set comprising TS, RS, SS and HS wipers has been advanced into engagement with any one of the terminal sets within a station line level, means comprising busy test relay BT i's eiective for determining whether or not the contactset so engaged is in its normal idle condition or has been made busy by other equipment in the office. A busy condition is indicated by the presence of ground on vthe one of the terminal sets engaged by wiper SS. lThe presence of battery potential on the same terminal indicates an idle condition. l

Assuming for the moment that the engaged terminal set is in busy condition and consequently that a ground potential has been appliedto wiper SS, a circuit for energizing relay BT is completed from wiper SS through break contacts CT 7, make contacts RDZ, break contacts SDI, make contacts PH6, break contacts 0F10 and the winding of relay lBT to battery. Relay BT thereupon operates. :1"

Returning to the point in time yat which relay SD released, upon the release or relay SD, the above traced operating circuit for relay PH is opened at make contacts SD3. Relay PH, a slow release type, is held operated for an interval of time sufficient to allow relay BT to operate over the above traced circuit. Relay PH thereafter re# leases to open the operating circuit of relay' BT atmakecontacts PH6.

Following the release of relay PH, a locking circuit for relay BTv is established from grounded conductor MG; through make contacts BTS, break contacts PHS and 0F10 and the winding of relay BT to battery.

.The operation of relay lBT is eifective at this time for connecting busy vtone to the calling subscriber linefiny order to inform the subscriber that the-attempted connection cannot be made owing to the busy condition of the "7 ditte.` 'The tone connection is `extended yfrom a grounded, loihtpedance busy ytone source (not shown) connctedit'o trniinalBYI through break contacts PHZ, make contct's "B'Tl, 'break contacts SW3, winding 1 of relay 'Aycap'aitor 'Cl, through the previously traced loop to eallingline station A comprising conductors T and R1 and winding 2 lof relay CBvto battery and thence to ground.

Swtchthroughfln the event 'that the terminal set engaged "by iwip'er SSoi the terminal set engaged by the wiper' -set is 'iin Aidle condition, the test terminal of the tin'l selector is prepared jfor a switchthrough operation, i. "e., a *completionfof the talking channel from the incoming lconductors'Tl Iand R1 `through blocking means comprising 'cpaeitors C1 `and C2. 'to the outgoing end of ,y

thesele'ctor channel comprising wipers TS and RS as well as Ythe 't'errninalsengagedby those wipers in the manner to be s'et foij'th presently. The blocking means is effective at this time to separate the direct current signaling circuit 'comprising the winding of relay CB connected to the incoming endof the channel from the outgoing end of the channel comprising wipers TS and RS. Upon engagement *of n set ot terminals by the wiper set, the absence oflgroundlpotential on wipers SS during the time that relay PH remains operated prevents the operation of relay BT over the above described circuit. Therefore, relay `BT remains unoperated and relay PH releases. A circuit is completed for operating switchthrough relay SW in response to 'the release of relay PH and the unoperated condition o'f relay BT. The circuit is traced from master ground through winding 1 of relay SW, break contacts BTG, PH7, `CT10 and SDI, make contacts RDZ, break contacts CT, "wiper SS, the terminal engaged wiper SS, to the resistance battery. Relay SW thereupon operates and completes a locking circuit for itself from grounded conductor MG `through make contacts SW7 and winding Z of relay SW to battery.

Theopera'tion of relay SW is effective for rendering well known `means `comprising ring trip relay RT effective to complete a circuit for energizing the well known alternoting current `signaling means at the called subscriber station such as C. This circuit is traced from the generator through winding 1 of rela'y RT, break contacts RT4, make contacts SWS, Wiper RS, through the conductor 12b of line 12 and the bridged alternating current responsive traced circuit including winding 1 of relay RT to allow relay RT to operate.

The operation of relay RT is effective for completing a locking circuit -for itself `from grounded conductor MG through make contacts ART11 and winding 2 of relay RT to battery.

The operation of relays SW and RT and the creation of the low impedance path between conductors 12a and 12b is etective for operating supervisory means comprising answering bridge relay AB. The operating circuit for relay vAB fs traced from ground through make con tacts SW2, winding -1 of relay AB, make contacts RTI and SW1, wiper TS, conductor 12a of called line 12, the low impedance path between the conductors 12a and `1Zb at station C, conductor 12b, wiper RS, make contacts SWS and RTS, and winding 2 of relay AB to battery. Relay -AB thereupon operates. The operation of 'foray AB L'the -diection of current ow` through the operating loop of relay CB at re veirigfcohtietsHIA-'Z and AB3=-4. The tif relay SW and the subsequent operation of RT is 'also effective "fo'rcompleting a connection between the talking channellbf the incoming 'end of the selector comprising conductors T1 and R1 randthe talking channel of the outgoing end of the selector comprising the wipers TS and RS. One side of this circuit is traced from conductor T1, break contacts CTZ, make contacts AB4, capacitor CZ, make contacts RTS and SWS to wiper RS; the other side of the talking channel is traced from conductor R1 through break contacts CTS, make contacts ABZ, capacitor C1, make contacts RTI and SW1 to wiper TS. With the incoming and outgoing ends connected in the previously described manner to calling line 10 and called line 12, respectively, station A is connected to station C and the signaling circuit which includes thc windings of relay CB is separated from the outgoing end or the final selector which includes wipers TS and RS by blocking capacitors C1 and CZ.

Trunk hunting in levels.-The iinal selector which includes the preferred embodiment of my invention is equipped for successively advancing the Wiper set comprising wipers TS, RS, SS and HSS over successive terminal sets within any one of the levels containing subscribers lines on the previously described switchthrough basis. Within each terminal set except the last in such a group, the terminals engaged by the S and HS wipers are strapped together. Thus, in all cases except the last terminal set within such a group, a busy indicating potential extended to wiper SS is also extended to wiper HSS.

In addition to the previously described means comprising make contacts CB1 of the impulse repeating relay CB, other means comprising hunt assist relay HA is provided for operating a secondary advancing means comprising secondary magnet S20. The previously described level marking XXB terminals corresponding to the levels in which station lines are terminated are employed in the following manner for completing a iirst circuit for energizing relay HA.

lUpon the engagement of a busy set within a group of terminals by Vthe main wiper set comprising wipers TS, RS, SS and HSS, the above-described circuit for operating relay BT is completed in the previously described manner. During the time that relay PH is in its operated condition, a rst circuit for energizing relay HA is completed from the busy indicating ground applied to wiper HSS, make contacts BTS, B wiring, the level marking XXB terminal, Wiper XX, break contacts 0F12 and S10,

make contacts PH9, break contacts SD7 and CT15, the winding of relay HA and break contacts HAI and R11 to battery. Relay HA thereupon operates and completes for itself a locking circuit from grounded conductor MG through make contactsI HAS, break contacts S19, make contacts PH?, break contacts SD7 and CTlS, the winding ot' relay HA and break contacts HAI and R11 to battery. The operation of relay HA is effective for completing an energizing circuit for maintaining relay PH in its operated condition. This circuit is traced from grounded conductor MG through make contacts HAZ, break contacts CTIZ and SD4 and the winding of relay PH to battery.

The operation of relay HA is effective in response to the operation of relay PH for closing an energizing circuit for secondary magnet S through make contacts HAZ and PHS and magnet S to battery. The operation of magnet S is effective at this time for advancing the wiper set out of engagement with the busy terminal set 'and into engagement with the succeeding terminal set within the group. The operation of magnet S is elfective for opening the above-described locking circuit for relay HA at break contacts S10, so that relay HA is released.

Following the advance of the Wiper set into engagement with the above referred to succeeding terminal set, the previously described busy test operation is repeated. ln the event that the terminal set currently engaged is in busylcondition, relay HA 'reoperatesand thereafter magnet S is re-energized as in the previously described manner.

armena n'the event that the terminal set is in idle condition,'no ground is extended over the above-traced circuit includ# ing lwiper HSS, sothat the above-described operating' circuit for relay HA is not completed. Relay HA fails to operate at this time, thereby opening the abovedescribed holding circuit for relay PH at make contacts HAZ for an interval of time sufficient to release relay PH. The release of relay PH and the presence of the idle-indicating battery potential on main wiper S is effective for operat''v ing SW in the previously described manner. The operation of relay SW is effective to complete the previously described alternating signaling circuit and to prepare relay RT for operation. Thereafter the call from station A to station C proceeds in the manner previously set forth.

In the event that all the terminal sets including the last within the called group are in busy condition, the absence of a strap between the terminals engaged by the SS and HSS wipers opens the previously described operating circuit for relay HA. The failure of relay HA to operatel prevents the further operation of magnet S and stops the advance of the wiper set in the secondary direction Within the selected level. Thereafter relay PH releases in the previously described manner and relay BT remains in its operated condition in order to provide busy tone to the calling line.

v Cut-through operation Two digit operation-Certain types of apparatus to which the calling subscriber line may have access by way of the selector forming the preferred embodiment of my invention may require an arrangement whereby a metallic connection is to be established between the conductors of the calling line and the conductors of the called line or trunk. Such trunks are usually arranged in groups so that it is necessary to provide means for advancing the wiper set of the final selector in its secondary direction over the busy ones of successive terminal sets within such a group. It may also be necessary to provide two digit operation,l i. e., for the selection of the first trunk in such a group after the directive primary and secondary movements of the main wiper set have been made in response to the transmission of rst and second directive signals to the selector.

In the final selector forming the preferred embodiment of my invention, trunks of the two digit type are termi.

nated in the tenth level. Means for bringing about cutthrough operations are also provided. In the preferred embodiment of my invention, the cut-through means are controlled by the above described level marking means. Accordingly, levels in which two digit trunks are terminated are characterized by D wiring connected to the appropriate XXB terminal for purposes to be explained presently. l

After the primary direction advance of the main wiper set to the tenth level and the subsequent secondary direction advance of the wiper set within that level has taken place in response to the transmission of directive signals to the nal selector, relay SD releases in the previously described manner. The release of relay SD is eifective for establishing the previously traced circuit comprising make contacts PH6 for rendering relay BT operative. Thus, the presence of busy indicating ground vpotential onthe terminal corresponding engaged by Wiper SS-of the engaged terminal set operates relay BT in the previously described manner. f

Within the tenth level group of trunk terminal sets, the terminals engaged by main wipers SS and HSS are strapped in the previously described way that corresponding terminals in the group of station line terminal sets are strapped. Thus, upon the advance of the wiper set into engagement with a busy trunk in a group of the tenth level trunks, a second circuit for energizing relay is completed as follows: from ground through wiper I-ISS, make contacts BT4, PHS and now operated secondary olfnormal contacts SON10, break contacts CT9 and RT7,

make v'contacts P-l, D wiring, the tenthXB terminal;`

HA operates and in the previously described manner completes the locking circuit for itself at make contacts HAS and the circuit for energizing relay PH and magnet S at make contacts HAZ. Thus, relay PH is maintained operated and magnet S is operated in order to advance the wiper set into engagement with the next succeeding terminal set within the group of trunks where the busy test is repeated. The main wiper set is advanced in this manner until an idle terminal set within the group is encountered, or until all terminal sets within the group have been found busy. t f

The operation of the secondary olf-normal springs upon the advance of the wiper set in the secondary direcminal through break contacts SON11 and CT9 at contacts SON11. The lower terminal of the relay CT winding is connected to ground through make contacts RDl-and` break contacts PD4 and BTZ.. The engagement of a busy terminal set by the main wiper set is effective to connect ground over the abovetraced. circuit comprising wiper HSS and make contacts BT4 to the upper winding of relay CT. The operation of relay CT is prevented at this time.

Upon the advance of the main wiper set into engagement with the terminal set of an idle trunk, ground is absent in the previously described manner from the HSS wiper, and consequently, the upper terminal of the relay` CT winding. The removal of the short from around the winding of relay CT allows cut-through means rcomprising relay CT to operate. The circuit for operating relay` CT is traced from ground through make contacts RD1,. break contacts PD4 and BTZ, the winding of relay CT,l break contacts RT7, make contacts PH4, D wiring, the XXB terminal, Wiper XX, break contacts 0F12 and S10, make contacts PH9, break contacts SD7 and CT15, the winding of relay HA, and break contacts HA1 and R11 to battery. Current owing through the windings of relays CT and HA in series is insufficient to operate relay HA, so that the latter relay remains released at this time.

The operation of relay CT is etective for establishing a locking circuit for itself from ground through make contacts RD1, break contacts PD4 and BTZ, the winding of relay CT, make'contacts CT14, the winding of relay HA, and break contacts HAI and R11 to battery. Similarly, the operation of relay CT is effective for opening its above-traced operating circuit at break contacts CT1S.

The operation of relay CT yis effective for maintaining relay PH operated from master ground through make contacts CT11, break contacts SD4 and the winding of relay PH to battery. Relay PH is held operated in order to maintain the operating circuit of relay CT closed at make contacts PH4 until the trunk circuit terminated on the set engaged by the main wiper set has been seized.

The operation of relay CT is also effective for transv ferring the incoming end of the selector talking channel comprising conductors T1 and R1 from its connection to the signaling circuit comprising the windings of relay CB into a direct metallic connection with outgoing end of the selector talking channel comprisingy wipers TS and RS.l The opening of the previously described connection be- CT, metallic connection is established between the calling. line yconductors and y the conductors connected to the `1l1 ones ofthe terminal set engaged bywipers TS and RS in order to provide an operating circuit for calling bridge relay CBA 'in the termination. The latter circuit is traced from ground through winding 1 of relay CBA, wiper TS, make contacts CTI, .conductor T1, thence over the previously traced calling line loop by way of the hookswitch contacts such asHltl at the calling station and back to conductor R1, and lthrough make'contacts CT4, wiper RS and winding 2 of relay CBA to battery. Relay ,CBA

thereupon operates. The operation of relay CBA is ef fective for completing an operating seizing means within the termination circuit such as release delay relay RDA from ground through make contacts CBAl and the wind ing of relay RDA to battery. The operation of reiay- RDA is effective for passing ground back to wiper SS in order to indicate a busycondition to iinal selectors other than the one shown `in Fig. 2 and for supplying ground potential to conductors-1 in order to lhold the calling line circuit and the linal selector in seized condition.

The above-described disconnection of the `windings'of relay CB from'the calling line conductors is effective for releasing that relay. The release of relay CB opens the operating circuit of relay RD at make contacts CB2. Rclay RD thereafter releases to open the above-described operating and holding circuits for relay CT at contacts RDI. Relay CT does not release at this time because conductor S1 is grounded from the succeeding trunk termination.` The release of relay RD removes ground from conductor MG in order to release relay PH.

Thereafter, the selector and trunk termination TT10 remain seized under the control ofthe calling line 10 and station A.

Single digit operadora- In addition to the two digit cut-through operation described above, it may be necessary operatc on a cut-throughbasis.v To this end, in the preferred embodiment of my invention, trunks accessible in response to the dialing of a single digit are 'shown terminated in the ninth level. lUpon the selection of the ninth level means comprising the .ninth terminal in the XB bank of terminals to which ground is connected by M wiring are effective for operating relay RT. VThe circuit is traced from ground through M wiring, the ninth XB termina., wiper X, break contacts SW7 `and PDS, make contacts CBS, break contacts RT10, and winding 2 of relay RT to battery. an obvious locking circuit `from master ground through make contacts RT11 for itself. Owing to the preliminary make nature of contacts RTll, the locking circuit is completed prior to the opening of the above traced operating circuit at break contacts RT10 so that there is no discontinuity in theoperation of relay RT.

Upon the primary advance of the main wiper setconrprising TS, RS, SS and'HS to the levelin which the single digit cut-through trunks are terminated, relay PD.releases in the previously describedV manner. At this time, relays SD and PH are maintained at their operated condition.

The ring trip relay RT used to` control signaling at the called station telephone ,in .the previously described manner is reused at this time a's meansfor 'controlling a circuit foroperating relay HA, Thus, the ,operation of the means comprising relay 'RT is Aeffective. in response to the operation of `relay PH for .completing a circuit for operating relay HA in orderyto advance the wiper set comprising TS, f RS, SS andHS "from Ithep'int '.opposite the ninth level of terminal sets into engagement with the .rst terminal set withinjtheA single d i'git level'. The circuit is Vtraced"frorrrfgrounl throughlrnake ebnf tactsRDl, break contacts 'PD4, BT2, "-SON11 and 'CT9,

make 'contacts RT, VC` wiring, 'terminal 9in -'the 'XXSA Relay RT operates and establishes i 12 bank, the wiper, break com-.ica 0F12 and stammte contacts PH9 and RT12, break contacts CT15, the windyingv of. relay HA and break contacts HAI and R11 'previously described manner for maintaining relay PH operated; contacts HAZ are also effective at this time, owing to the operated condition of relay SD, for completing a locking circuit for relay Si) through make contacts' PHS and SDS and winding 2 of relay SD to battery.A

The operation of magnet S is effective for advancing the wiper set into engagement with the first terminal set in the selected ninth level. Upon the engagement of thc rst trunk,` a test circuit is completed for determining whetherl or `not the terminal set so engaged is in busy condition. As in the case of the above-described tenth level trunks, a busy condition is indicated by the presence of a groundpotential on the one of the engaged terminal sets engaged by wiper SS. The presence of busy potential on w'iper SS is effective in response to the operation of relays RTand SD for completing a third circuit for energizing relay HA which is traced from wiper SS through break contacts CT7, make contacts RDZ and SDZ, C wiring, the ninth'terminal inthe XXB bank, the XX wiper, break contacts 0F12 and S10, make contacts PH9 and RT12, break contacts CT 1S, the winding of relay HA and break contacts HA and Ril to battery.

Prior to the secondary direction advance of the main wiper set into engagement with the first terminal set in the ninth level, a circuit is completed for snorting out the winding of relay CT in order to prevent tlie latter relay from operating, from tbc lower winding terminal of relay CT through break contacts SONli. and CT9 to the upper winding terminal of relay CT. Upon the ad- Vance of the main wiper set in its secondary direction, secondary off-normal means comprising break contacts SONll are leffective to open the short and to interrupt the original energizing circuit for relay HA. Thereafter, ground potential applied to the busy testvcircuit comprising wiper SS is effective for continuing to short ontlthe relay CT winding. The busy test ground is cxtended to the Upper winding terminal of relay RT over the following circuit: from wiper SS through break contacts Cl`7, make contacts RDZ, ST2, and RT to the upper windingterminal of relay CT.

Upon the engagement of the idle terminal set. the shorting ground extended to the upper winding terminal of relay CT `is removed. Relay CT now operates over a circuit traced from ground through make contacts RDI, break contactsfPD-l and BT2, the winding of relay CT, make contacts RT6, C wiring, the ninth terminal in the XXB bank, the XX wiper, break contacts OF 12 and S10, makescontacts'PI- and RT12, break contacts CTiS, thc winding o'f relay` 'HAand break contacts HAI and Rll to battery. -As in the previously described case, thc connection of the windings of relays CT and HA in series across battery and ground is effective for operating rclay CT but not operating relay HA. In response to the operation of the secondary olf-normal means and thc continuing releasedcondition of relay HA, the `holding,r circuit for relays SD and PH is opened at contacts HAZ .for aftimelintcrval to allow the'latter relays to release.

' channel "at contacts' CTZ and'CTS and forestablishing a meeste ltalkingy channel comprising conductors T1 and R1 to wipers TS and RS at make contacts CTI and CT4," respectively.

The operation `of relay CT and the resulting establishment of a Vconnection from the conductors of the calling line to trunk TTI is effective for operating repeating means comprising calling bridge relay CBB within the termination over the loop comprising the conductors of the calling line circuit. The circuit for operating relay CBB is traced from ground through the windings I of relays CBB andk SR, wiper TS, make contacts CTI Iand conductor R1, thence over the previously traced circuit comprising the conductors of the calling line I and hookswitch contact such as H atthe calling station and returning over conductor R1 through make contacts CT4, wiper RS, and the windings 2.v of relays SR and CBB to battery.

The disconnection of the windings `of relay CB from conductors TI and R1 causes the release of relays CB and RD in the previously described manner. The release lof relay RD is effective for removing ground potential from the master ground lead, thereby opening the locking circuit of relay RT, which thereupon releases. However,

the operation of relay CBB is eifective for completing an operating circuit 'for relay RDB from ground through break contacts RSI, make contacts CBBS, and the winding of relay RDB to battery. Relay RDB operates to pass ground back through the previously traced operating circuit including wiper SS for holding operated relay CT in the selector circuit.

Service restriction-The selector fonming the preferred embodiment of my invention is effective for extending connections from all the subscriber lines in the system to any one of the subscriber lines or trunk circuits in the manner set forth in the foregoing description. However, the'subscriber lines in the contemplated system are divided into` restricted and unrestricted classes. Thus, line 10 terminating in circuit LC10 is an example of a line to which unrestricted service is to be given.

Service restrictions are imposed in the preferred embodiment of my invention only in the case of connections extended over the trunks terminated in -circuits such'as TTII. Such trunks are shown terminated in the ninth level which is accessible in response to the dialing of a single digit into the selector. However, it is to be understood that such service restrictions might also be provided on trunks or lines terminated in other levels where those rtrunks or lines are accessible in response to the dialing of two directive signals into the selector and the digits are eifective for causing the main wiper 'set to be advanced in primary and secondary directions into engagement with a particular terminal set. Referring to selector loperation on a single digit basis, terminations such as TTII include means 'comprising the calling bridge relay for repeating directive signals originating at the calling line station tothe trunk line such as T11 extending to a distant otiice. The service restriction in the preferred embodiment of my. invention is fthe preventing of the extension of connections-from linesof the restricted class lonly to certain destinationsy such 'as toll operator positions, where the particular destination is reached by transmitting particular codes of signals as la first digit 0.

The seizure of a trunk-in the ninth level is elfected in the previously described manner by operating relay CBB over a loop circuit including the windings of relay CBB, the talking channel .conductors of the final selecto-r,the callinglline,'and the calling line station. As previously pointed out, the operation of relay CBB is eifective for operating release delay relay RDB from ground through break contacts RSI, make contacts CBB3, and the winding of relay RDB to battery.

VThe operation of-.relays CBB and RDB is effective for starting the seizure process of trunk TII -to` the distant oiceby completing fan operating circuit' for shunt relay SH from ground through break contacts SWBS, make con- 14 mets RDBl and the winding of relay Relay SH thereupon operates.

The operation of relay'RDB is effective for operating release delay repeater relay RDP at make contacts` RDB2. Relay RDP thereupon operates. The 'operation `of relay RDB is effective for operating ntf-normal relay ON. The circuit is tnaced from ground through make contacts RDBZ, break contacts MGN and the winding of relay ON to battery.

The operation of relays SH, RBD, and CBB is eifective for seizing trunk T11 by completing an incoming signal circuit to the distant oiiice.

from ground through mlake contacts SHI, the winding of relay SG, make contacts CBBI and RDB4, conductor TIIb of trunk T11 thnough seizure responsive means 'at' the distant office, thereby seizing distant folice equipment. The seizure of the distant oiiice equipment is effective for placing ground potential on the trunk conductor Tlla in forder to complete an `operating circuit for vswitchthrough relay SWB. The circuit is traced from ground through the distant oice equipment, conductor T1141', make contacts RDBS, break contacts SWB3, and the wind-- ing of relay SWB to battery. Relay SWB thereupon operates.

The operation of relay SWB is effective for transferring the winding or" relay SG from its previously described connection to ground through make contacts SHI to con-l ductor TIIa and the distant oiiice ground source at break contacts SWBZ and make contacts SWBl. Owing to the make before break nature of contacts SWBI and SWBZ, this transfer is eifected without releasing relay SG. The operation 'of relay SWB is also effective for disconnecting its own winding through the previously described operating circuit at break 4contacts SWB3 and connecting its winding to la holding circuit from ground thro-ugh make contacts SGI and SWB4 and the winding of relay SWBy to battery. The operation of relay SWB is also effective for opening the operating circuit fof relay SH at break contacts SWB6 and for applying ground to the wiper SS of the nal selector at make contacts SWBS.

Returning to the circuit for operating relay CB, it is pointed fout that the latter circuit includes the windings of service'restricting relay SR. The relay SR windings are of equal inductvance and are wired into the circuit differentially so that equal and `opposite fields induced in the frame of the yrelay by current owing in the group comprising the subscribers line do not operate relay SR. Following the seizure of termination TTll, the operation of relvay RDP is eifective for shorting out the windings of relay SR at make contacts RDB2. and RDP3. Therefore, if relay SR is to be operated, the conditions for operating it must occur after the circuit for operating relay CB has been completed but before the operation of relay RDP. v

Assuming that termination TTII has been seized from a calling line of theA unrestricted class, upon the transmis` sion of a signal from the calling station dial in the previously described manner to the signal repeating' means comprising relay CBB, relay CBB repeats impulses 'over the loop of trunk Till comprising conductor Tlln, make contacts SWBI, ythe winding of relay SG, make contacts CBBI land RDB4 and conduct-or TIIb by repeatedly openingv and reclosing make contacts CBBI. in this manner, the repeating means is elective for repeating an indefinite number `of directive signals lof any value yto the distant office. l

` ln the case of calls extended from lines of the restricted class to the termination TTI, it is necessary to momen'- tarily unbalance the loop of the operating circuit for relay CBBy in order to indicate to termination TTII that the call isrv extended from a restricted service line. The unbalancing' ofthe loop of relay CBB is accomplished by connecting ground tothat part of the loop associated withthe upper winding of relay CBB and is eective to SH' y to battery.

The latter circuit is also effective for operating signal relay SG and is traced` make unequal current now through windings 1 and 2 of relay SR prior to the operation of relay RDP. 'l`he method by which the unbalance of the loop is accomplished is next described.

Returning to the consideration of the line circuits and the nal selector, lines of the restricted type or class are terminated in line circuits such as LC10 to wherein a ground connection is extended to the nder bank termirial H512. The corresponding terminal, HS11, in the terminating circuits of each unrestricted type line is left ung'r'oundcd as shown in the case of line circuit LCll.. When a call has been extended from a restricted type line such as L10 through line finder LF 10 into the final selector, ground from the restricting terminal H812 is extended through wiper HSF to conductor HSL Following the operation of relay CT and the release of relay RT but p ior to the release of relay PH, means comprising a circuit for unbalancng the previously described operatlng -loop of relay CBB is actuated in order to operate the service restricting means comprising relay SR within termination TTl. This circuit is completed upon the advance of the main wiper set of the selector to the termi tial set to which trunk termination TT11 is connected (i.- e., before slow operate type relay RPD has had 4time to operate). The unbalancing circuit is traced from ground through terminal HS12, wiper HSF, conductor HSI, make contacts CT17 and PHI, break contacts RTS, wiper TS, the windings 1 of relays SR and CBB to ground. The shorting out of the upper windings of relays SR and CBB is effective in the previously described manner to allour current to tlow in only winding 2 of relay SR so that the latter relay operates at this time.

The operation of relay SR is eifective for completing an operating circuit for service restricting repeater relay SRP from ground through make contacts RDB3 and SR1 and the winding of relay SRP to battery. Relay SRP' Vthereupon operates and locks itself up through an obvious circuit including make contacts SRPl.

The operation of relay SRP is etiective for rendering digit counting means comprising a minor switch effective. Thus, upon each release of relay CBB during the repeating operation, a circuit for energizing the stepping magnet MX of the minor switch is completed from ground through break contacts RSI. and CBB2 and make contacts RDBI and SRP2 and the winding of magnet MX to battery. The impulsing of magnet MX is effective in thc well known manner to drive minor switch wiper MW from its normal position into engagement with the one of the minor switch bank terminals corresponding to the number of impulses in the repeated train as indicated by the number of operations of magnet MX.

The advance of the minor switch wiper away from its normal position is effective for opening the above described operating circuit for relay ON at break contacts MON. Thereafter', during the repetition of impulses (i. c., when relay SH3 is operated in response to the impulsing operation of relay CBB), relay ON is maintained in its operated condition from ground supplied through make contacts RDBZ, SH3 and ONl. Upon the stopping ofv the repeating operation of relay CBB, relay SH is released in the previously described manner to open the holding circuit of relay ON at make contacts SH3. Relay ON2 thereupon releases.

ln the event that the directive signal has been transmitted` from the restricted class calling line, which is effective for directing the central oiiice vequipment to a forbidden destination, minor switch wiper MW is-a'dvanccd to a bank terminal connected to the winding of restricted service relay RS. The minor switch is effective under these conditions for completing an operating .circuit for relay RS which is traced as follows: from ground through `trial- :c contacts RDB2, break contacts ON2, short ingbar MSB, wiper MW, and the winding of relay RS to. battery. Relay lRS thereuponoperates.

The operation of restricting relay RS isetectivc for 1 "5 opening the previously traced operating circuit for relay RDB at break contacts RSI. Relay RDB therefore re lleases at this time.

The release of relay RDB is effective for opening the previously traced loop to the distant otiice for operating signal relay SG at make contacts RDB4. Relay SG thereupon releases, opening the operating circuit of relay SWB at make contacts SG1. Relay SWB releases.

The release of relays SWB and RDB is effective for removing ground from the operating circuit of relay SRP and the wiper SS of the previously described iinal se lector switch. Relay SRP thereupon releases. In response to the removal of ground from wiper SS, the iinal selector switch is released in a manner to be described.

Release of the selector Upon the completion of a call, either to a station line or to a trunk, the release of the final selector switch is brought about by the release of the connection under the control of the calling subscriber. In the case of a call extended to a station line wherein relay CB within the final selector is held throughout the call under the control of the calling subscriber station, return of the calling station telephone to its hookswitch and the consequent opening `of the hookswitch contacts, such as H10, is effective for releasing relay CB, thereby opening at make contacts CB2 the previously described operating circuit for relay RD. Relay RD releases at this point to remove ground potential from grounded conductor MG at make contacts RDS. The removal of master ground is eiiective for opening the operating circuits for relays SW, RT as well as relays PD, SD, and PH if the latter are still operated.

The release of relays RD and SW is effective at this time for completing an operating circuit for release magnet R. The circuit is traced from ground through break contacts SWS, RD6 and CT16 and either of operated oli-normal springs PON11 or SON12 and the winding of magnet R to battery. The opeartion of magnet R is eiective in the well known manner for restoring the wiper set comprising TS, RS, SS and HSS, thereby opening the connection between the calling subscriber line anda called subscriber, and for restoring auxiliary level marking wiper AW to their normal positions. Other means (not shown) restore the line finder wiper set comprising wipers TF, RF, SF, and HSP to its normal position in order to disconnect the calling line from the incoming end of the final selector.

In the case of calls extended to one of the cut-through type trunks, it is to be recalled that only relay CT remains in its operated condition after the connection has been established and that the locking circuit for relay CT includes a ground connection from the succeeding equipment such as trunk termination TT10 extended over main wiper S. The restoration of the telephone at the calling station such as A to its hookswitch is effective for opening the .operating circuit of the trunk circuit calling bridge relay such as CBB, the' equipment succeeding the linal selector. The release of the calling bridge relay releases the associated release delay relay such as RDB in order to remove ground from the wiper SS of the final se lector at contacts such as RDB3. Relay CT within the nal selector thereupon releases.

The release of relay CT is elective at this time for energizing the release magnet R by completing the above traced operating circuit for magnet R at break contacts CT16. The operation of relay R is effective in the previously described manner to restore the wiper set and auxiliary wiper AW to their normal positions and thereby interrupt the connection extended `between the calling line and the succeeding trunk termination. Similarly, the line finder LFI() is released vto disconnect the callingline from the iinal As ele ctor.

AWhile-lhave shown and described a particular embodiment `of my invention, it will be obvious tothose skilled inthe art that changes and modifications may be made without departing from Vmy invention in itsv broader aspects. I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What is claimed is:

l. In a telephone system including a calling line, a yselector including a set of wipers, and means for extending a connection from said line to said selector and seizing sai-d selector, wherein said selector includes a plurality of terminal sets arranged in a plurality of levels including a particular level, means connected to each of said terminal sets for changing the connected terminal set froml its normal idle condition to a busy condition, rmeans operative in response to the transmission of a irst directive signal to said selector for advancing said wiper set in a primary direction to select any one of said levels, means to be energized for advancing sai-d wiper set in a secondary direction into engagement with any one of said terminal sets in a selected one of said levels, a circuit for energizing said secondary advancing means, means operative in response to the seizure of said selector for preparing said energizing circuit, means operative in response to the transmission of a second directive signal to Said selector and to the operation of said preparing means-for completing said energizing circuit in order to advance said wipers set into engagement with a particular one of said terminal sets, and means for releasing said preparing means at the conclusion of the secondary advance of said wiper set, the combination comprising: other means for completing said energizing circuit, busy test means operative in response to the release of said preparing means and to the selection of an indicated busy one of said terminal sets for completing an operating circuit for said other means, and means operative in response to the selection of said particular level together with the operation of said preparing means and the engagement of a busy one of said terminal sets for preparing another operating circuit for said other means, whereby said secondary advancing means is prepared for operation at the conclusion of a directive primary movement of said wiper setto said particular level and'may be furtheradvanced at the conclusion of directive primaryl and secondary movements of said wiper set toa set of busy terminals within one of the other of said levels. l i 2. The telephone system' set forth in claimV lv and having in addition off-normal means having an operated condition in response to the advance of said wiper set in its secondary direction, and means operative in response to the unoperated condition of said o-normal'means Yand to the selection of said particular level for completing still another circuit for said other means, wherebyl saidwiper set is advanced into engagement with the rst of said terminal sets within said particular level at the conclusion of a primary movement of said wiper set to said first, level.

3. In a telephone system including a calling line, aselector including a speech transmision channel and avsetof Wipers, and means for extending a connectionfrom-said line to said selector and for seizing said selector, wherein said channel includes an incoming end connected to said line by said connection extending means and an outgoing end comprising certain ones of said set of wipers, a signaling circuit, cut-through means normally effective for connecting said incoming channel end to said signaling circuit, blocking means normally effective for separating said signaling circuit from said voutgoing channel end, switchthrough means for completing a connection from said incoming end to said outgoing end through said blocking means, said cut-through means being operative for completing a metallic connection between said calling line and'said outgoing end, a plurality of terminal sets arranged in a particular first, a particular second, and other levels, said terminal sets in said lirst level and certain consecutive ones of said terminal sets in said second and said other levels being arranged in groups, means connected to' eachl of said terminal sets operative for changing th'e connected terminal set from its normal, idle conditin to a busy condition, means operative in response to a first directive operation of said signaling circuit for advancing said wiper set in a primary `direction to select any one of said levels, means for advancingV said wiper set inv a secondary direction into engagement with any one of said terminal sets in a selected level, acircuit` for energizing said secondary advancing means, means'V operative in response to the seizure of said selector for preparing said secondary advancing circuit, and means operative in`-response to a'se'cond directive operation of said signaling circuit andthe operation of said preparing means for completing said secondary advancing circuit in order to cause said wipers to engage a particular one of said terminal sets within a-selected level, and means operative in response to the secondary advance of said wipersV for releasing said preparing means at the conclusion of a secondary advance of said wiper set, the combination comprising: Vother means for completing said energizing circuit, busy test means operative in response to the selection ofra busy one'of said terminal sets and to the release of said preparing means, means operative in response to the operation of said busy test means and to the Aselection of one of said other levels for completing a first operating circuit for said other means, means normally operative in response to the unoperated condition of said preparing means andthe release of said busy test means for completing an operating circuit for said switchthrough means, means operative in response to the selection of said second level for preparing a iirst operating circuit for said cut-through means, said second level selection responsive'means being operative in response to the operation of-said busy test means for completing al second operating circuit for said other means effective in the presence of a busy .condition on the terminal set engaged by said wiper set for preventing the operationof said` cutthrough means, means operative in response to the selection of said tirst level for preparing a second operating circuit for said cut-through means, olf-normal means'having a normal condition operative in response to the advance of said wiper set in its secondary direction, saidfirst level selection responsive means being` operativey in response tothe normal condition of said oli-normal means for operating said other means to advance said wiper Vset into engagement with said first terminal set within said first level, said second level selection responsive means being thereafter operative in response to the operation of said preparing means and to the engagement ofja busy one ofv said terminal sets for completing a third operating circuit for said other means, the energization of said third operating circuit being effective forV preventing the operation of said cut-through means. l n y 4. In a telephone system comprising aline, means connected to said line for seizingand thereafter transmitting directive signals over'said line, a trunk, a circuit comprising 'repeating means and seizure responsive means for terminating said trunk, said repeating rneansbeing elective for operating said lseizure responsive means and being thereafter. operativefor seizing vand repeating directive signalsl to said trunk, a selector `having a normal ,condition and operativeinrespon'se'to signals transmitted from said line for selecting said trunk, means in said selector having a normal condition operative in response to the selection of said trunk for connecting said repeating means to said line in order to render said repeating means operative in'response to signals transmitted over said line, said seizure responsive means being effective for thereafter maintaining said selector connecting means in operated condition, means in said selector thereafter operative in response to the operated condition of said selector and the normal condition of said connecting means for restoring said selector to normal condition, the combination comprising: means operative to any one of a plurality of unique conditions for registering the value of ai directive signal, said repeating means being operative for operating said signal registering means to one of its unique conditions corresponding to the value of a signal repeated to said trunk, and means responsive to a particular operated condition of said repeating means for restoring said seizure responsive means to normal condition, whereby said selector connecting means and said selector are restored to their normal conditions and said trunk is released following the transmission of a particular directive signal over said trunk.

5. In a telephone system comprising a first line ter` minating in a line circuit of afirst class, a second line terminating in a line'fcircuit of a second` class, lmeans individual to each of said line circuits for seizing and'thereafter transmitting directive signals over the corresponding one of said lines, a trunk, a circuit comprising repeating means and seizure responsive means for terminating said trunk, said repeating means being effective for operating said seizure responsive means and thereafter operative for seizing andrepeating directive signals to said trunk, a selector having a normal condition operative-in response to` the seizure of and the subsequent transmission of 'directive signals from either of said lines `for extending a connection from the seized one of said lines to said trunk, means in said selector having a normal condition and operative in response tto the selection of said trunk for connecting the seized one of said linesto said repeating means in order to render said repeating means operative in response to signals transmitted from the yseized one of said lines, said seizure responsive means being effective thereafter for maintaining said selector connecting means in operated condition, and means in said selector subsequently operative in response to the operation of said selector and to the normal condition of said selector connecting means for restoring said selector to normal condition, the combination comprising: means in said termination having a plurality of operated conditions for registering the value of a directive signal, means operative in response to the extension of a connection from said lirst line to` said trunk terminating circuit only for render-g ing said repeating means operative to advance said registering means to the one of said operated conditions corre-` sponding to the value of a signal repeated to said trunk, and means `responsive to a particular operated condition of said 4repeating means for restoring said seizure responsive` means to normal condition, whereby said connecting means and said selector are restored to normal condition and said trunk is released following the transmission of a particular directive signal from said first line over said trunk.

6. Ina telephone system comprising a first line terminating in a line circuit of the first class, a second line terminating in a line` circuit of the second class, means individual to each of said lines receiving and thereafter transmitting directive ysignals over the corresponding one of said lines, a trunk, a^ circuit comprising repeating means and seizure responsive means for terminating said trunk, said repeating means being effective for operating said seizure responsive means and thereafter operative for seizing and repeating directive signals to said trunk, a selector having a normal condition comprising a talking 2i) channel and a class of service conductor, means operative in response to the seizure of either of said lines for connecting the seized one of said lines to said channel in order to seize said selector and for connecting the one of said line circuits terminating the seized one of said lines to said class of service conductor, means individual to said first class of line circuit for energizing said class of service conductor, means for causing said selector to advance to said trunk termination, means in said selector having a normal condition operative in response to the seizure of said selector for rendering said advancing means operative, other means having a normal condition operative in response to the selection of said trunk termination and to the operation of said seizure responsive means for further extending a connection from said channel to said repeating means in order to render said repeating means operative in response to signals transmitted from the seized one of said lines to said trunk termination, means operative upon the advance of said selector to said trunk termination for restoring said selector seizure responsive means to normal condition, and means operative in response to the advance of said selector and the normal condition of said selector connecting means for restoring said selector to normal condition, the combination comprising: means in said termination having a pluraltiy of operated conditions for registering thevalue of a directive signal, means for rendering said repeating means operative for advancing said registering means to the one of said operated conditions corresponding to the value of a signal `repeated over said trunk, a circuit completed in response to the operation of said other means and said selector seizure responsive means for connecting said class of service conductor to said channel, and means operative to a particular operated condition of said repeating means for restoring said trunk circuit seizure responsive means to normal condition, and means connected to said repeating means operative in response to the completion of said connection for rendering said registering means operative.

l7. The system set forth in claim 6 wherein said line includes lirst and second conductors, said repeating means includes a relay having first and second windings in series with said conductors, and said means connected to said repeating means includes a relay having first and second windings differentially connected in series with said conductors, whereby the completion of said circuit is effective for unbalancing the flow of current through said first and second windings of said dilferentially wired relay in order-to cause said differentially wired relay to operate,

8. The system set forth in claim 6 wherein said termination includes means operative following the operation of said termination seizure responsive means for rendering said means connected to said repeating means inoperative, and means for maintaining said registering means operative until a first operation of said repeating means is completed, whereby said registering means is effective for rlelgil'lslering the value of a first signal transmitted to said t No references cited. 

